The present invention relates to high voltage circuit breakers and, more particularly, to magne-blast, vertical racking circuit breakers.
Power supply systems are protected by switchgear which includes a circuit breaker. One type of circuit breaker, used in combination with medium range, metal-clad switchgear, is the magne-blast circuit breaker. A magne-blast circuit breaker includes contacts which separate when the breaker is opened, and the arc which extends between the open contacts is interrupted by elongating the arc and forcing it into an arc chute where the arc is cooled. The arc is drawn into the arc chute by means of a strong magnetic field and a blast of cooler air; the air serving the dual function of directing the arc into the chute and cooling it.
Use of magne-blast circuit breakers with metal-clad switchgear has provided advantages of protection to equipment and personnel, compactness, simplified installation and reduced maintenance. However, magne-blast breakers have the disadvantage of requiring arc chutes made of asbestos, which is vaporized somewhat when brought in contact with an arc.
New circuit breakers have been developed in which the breaker elements are enclosed in a vacuum envelope made of a high-density alumina of ceramics or glass. Consequently, the arc produced by the separated contact elements is minimized and enclosed in a sealed bottle. While such vacuum interrupters have many desirable characteristics, among them the elimination of asbestos material, much of the switchgear existing today is specially adapted to receive the earlier magne-blast circuit breakers. One such example of an earlier magne-blast breaker is the General Electric Model AM-13.8-3 magne-blast circuit breaker, which is a vertical racking unit; that is, the load and line stabs of the circuit breaker extend vertically from the main frame of the circuit breaker and are received by the switchgear by elevating the circuit breaker vertically. Accordingly, there is a need for modifying magne-blast vertical racking circuit breakers to receive the more desirable and reliable vacuum interrupters and yet interface with the magne-blast switchgear.